Duels is a Seasonal Event where two players fight with a Brawler selected from a trio of Brawlers. The objective of the game is to defeat all of the opponent's 3 chosen Brawlers in a series of rounds. If your Brawler defeats an opponent's Brawler, they will be transferred to the next round and face another one of the opponent's Brawlers. The game ends in a draw if both of the players' third Brawlers are defeated at the same time. After a period of time without ending a round, a poison gas, similar to the one in Showdown, blows from all edges of the map, which serves as a tiebreaker for whoever survives first. Note that both Gadget charges and Supers (except for Meg's Mecha Super) carry from Brawler to Brawler, meaning using a Gadget twice when playing your first Brawler means that your next Brawler will only have one Gadget charge. Brawlers will also gain and lose roughly 1/3rd of the Trophies normally gained in a 3v3 Event.
- Darryl: Darryl is a relatively well rounded Brawler as he can deal with Tanks and longer-range Brawlers, making him a fine first pick. He can wait for the majority of a round and charge his super automatically, allowing for him to use his Super to roll onto a Brawler later and deal devastating damage up close. This is successful a majority of the time regardless of the opponent. He can also carry his Super to the next round if defeated, which is especially useful because it charges passively. This strategy can also be applied to Edgar, though if using him you might want to save a Super for the next round when facing a tank that might defeat Edgar regardless.
- Gale: Gale is a fine pick for the Duels mode. One can use his Super to counter short range aggressive Brawlers, like Mortis or Buzz. This makes him fine when picked in a team that also includes vulnerable Brawlers. His Freezing Snow Star Power is very good at chipping down opponents to get his Super. Chip down opponents to get his Super, and wait (usually behind a wall) for the poison clouds to close in, and use his Super to push them into the poison so they take damage. Attacking them with the Freezing Snow Star Power keeps them in the poison longer as well. In addition, Gale's Twister Gadget can be used to counter short-ranged Brawlers such as Mortis, Buzz or Edgar.
- Leon: With Leon's invisibility and range, taking out enemies should not be difficult. His Super allows you to rush enemies, and sneak up to them with it. Previous Brawlers with fast-charging Supers can let Leon start the match with a major advantage, allowing you to quickly eliminate an otherwise troublesome enemy Brawler.
- Tara: Tara's attack range allows her to slowly chip at the enemy Brawler, and her Super can keep them from attacking for you to quickly gain an upper hand. If Tara has her Support from Beyond Gadget, she can easily overwhelm Brawlers whose attacks fire a single projectile, using them as shields as she charges into the enemy or to give you some time to retreat when at low health.
- Stu: Stu has high burst damage potential, great mobility with his Super, and can charge his Super with just one hit. This allows him to chain supers easily by attacking and then using his Super afterwards. This is very helpful when trying to avoid shots from sharpshooters that out-range him, as his Super allows him to easily dodge their shots. Stu's Speed Zone Gadget increases his movement speed, allowing him to travel across the map and avoid shots easier. Alternatively, his Breakthrough Gadget can help Stu bypass walls, though keep in mind that the enemy can also pass through later if they are not defeated yet.
- Piper: Sharpshooters work well in more open maps, but Piper can still get her Super and break obstacles if necessary. Her Homemade Recipe Gadget aids in hitting her attacks on really open maps, while her Ambush Star Power allows Piper to deal additional damage.
- Crow: Crow's poison can pressure the enemy and if the enemy cannot deal enough damage to defeat Crow, they must retreat. In addition to getting closer to sharpshooters like Piper or escaping from enemies, Crow's Super is also good at checking bushes. Crow's Defense Booster Gadget allows him to take more damage, especially since his health is quite low. On the other hand, Crow's Slowing Toxin Gadget helps him get closer to enemies without his Super and to defeat them faster if they do not have another mobility ability.
- Edgar: Edgar has a huge advantage due to his trait. He does a lot of damage and both of his gadgets are very helpful in this game mode. Your enemies are most likely to choose an assassin so the damage gear and the speed gear are the best for Edgar. His super charge is fast so if you die while attacking you will spawn in with your next character and its super attack.
- Pick Brawlers who can charge their Supers quickly at the beginning of the match like Stu, Darryl, Edgar or Buzz, as your first Brawler can give you a big advantage especially since their Supers, if fully charged at the end of a round, remain charged when the next round starts. Keep in mind that if their Supers were charged if they're defeated, the next Brawler has their Super fully charged.
- Brawlers who can get up close to the enemy very quickly that also have high burst damage (like Surge, Buzz, or Edgar) are great in Duels, especially against Brawlers with moderate health or lower.
- To counter this, players can pick Brawlers with abilities that provide slows, stuns, or other defensive abilities such as Gale's Super or Lou's Ice Block Gadget, or Brawlers that can deploy a spawnable, like Nita, Jessie and Spike. All three of them can quickly counterattack with high damage, easily taking down the now vulnerable enemy.
- For the second and third Brawlers, you can pick a Brawler that has a high-damaging Super, like Nani or Meg, a Super that can provide pulls or knockbacks like Tara's, or a brawler that has a super with great self utility such as Leon's.
- If you are facing against a Brawler that you are near certain you will lose against no matter what, and you have your Super charged, it can be useful to save your Super for the next round instead of wasting it in a last-ditch attempt to win.
- When creating a Brawler composition, make sure that your second Brawler counters most Brawlers that your first Brawler will lose against, and your third Brawler should counter most Brawlers that your second Brawler will lose against, so that you may counter a wide range of opponent Brawlers.
- Try not to pick throwers (especially on open maps) because they can be countered by a lot of assassins that excel in the mode. If you pick a thrower as one of your Brawlers, pick a defensive Gadget and/or Star Power (like Barley with Sticky Syrup Mixer or Tick with Last Hurrah) to distance the enemy from you.
- On 16/12/21, Duels was temporarily added to the game during Brawl Pass Season 10.